This invention generally relates to lids for liquid-containing cans, and more particularly relates to pre-formed lid constructions for cans which permits the cans to be opened without the use of can openers. The prepared opening in the can lid will be hereinafter called an "aperture", the structure which initially covers this aperture will be called a "gate," and the invention set forth herein will be generally referred to as a "gated can lid." This invention further specifically relates to an improvement in the gated can lid structure disclosed in U.S. Pat. No. 3,334,775 issued Aug. 8, 1967.
In U.S. Pat. No. 3,334,775, a gated can lid is disclosed of the type wherein a continuous blank of a planar or flat sheet metal member is drawn and shaped so as to provide an aperture in the surface of such member and a gate panel underneath the aperture adapted to normally close same, the so-shaped sheet metal member defining a lid for attachment to the walls of a liquid-containing can, for example. The construction of the lid is further such that the gate panel disposed underneath the aperture can be opened through the application of downward pressure thereupon so as to thus facilitate emptying of the contents of the can.
To this end, the construction of the gated can lid of U.S. Pat. No. 3,334,775 is such that the surface of the lid is underfolded about the edge of the aperture as a 180.degree. outward underfold to form a narrow spacer strip at the under side of the lid about the edge of the aperture, the metal sheet thence being infolded about the outer edge of the spacer strip as a 180.degree. inward underfold to merge into the metal sheet portion constituting the gate panel, a score line being cut about the edge of the gate panel adjacent to the 180.degree. inward underfold which is adapted to permit the gate panel to be severed from the spacer strip and pushed downwardly into the can by the application of pressure thereon.
The gated can lid of U.S. Pat. No. 3,334,775 constituted a marked advance in the art which enabled the economical construction of pre-formed can lids having prepared openings therein. As successful as such construction has been, however, certain disadvantages thereof have now been discovered. For example, in such prior construction, the underfolding of the sheet metal member was contemplated to take place about the entire periphery of the aperture, even at such portion of the aperture which defined a hinge which served to maintain the gate panel in attachment with the can lid after the gate panel had been opened by the application of downward pressure thereto.
In those embodiments of the gated can lid wherein the aperture was located near the periphery of the lid, i.e., near the edge of the lid which was attached to the can body by means of a folded interconnecting seam, it has been found that the metal drawing operation necessary to provide such underfold might adversely weaken the interconnecting seam and adjacent area, this weakening bringing about an increased risk of leakage of the contents of the can.